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A combination of inactivated sodium channel blockers causes competitive interaction on dV/dtmax of single ventricular myocytes.

STUDY OBJECTIVE: The aim was to study an interaction between class I antiarrhythmic drugs on the cardiac sodium channels. DESIGN: The single pipette, whole cell clamp method was employed to control and record membrane potential. The maximum upstroke velocity (dV/dtmax) was measured as an index of sodium channel availability during treatment of the preparations with aprindine (5 microM) in combination with mexiletine (40 microM), and lignocaine (40 microM). EXPERIMENTAL MATERIAL: Single ventricular myocytes (n = 6-8 per experiment) isolated from guinea pig hearts were used. MEASUREMENTS AND MAIN RESULTS: Trains of depolarisation to 0 mV (0.2-2.0 Hz) were applied from the resting membrane potential (-85 mV) following a long quiescent period to evaluate "tonic" and "use dependent" decrease (block) of dV/dtmax. Additional application of mexiletine or lignocaine to aprindine resulted in an increase of tonic block and a decrease of use dependent block. Because of such counteracting action, the steady state dV/dtmax during the train of depolarisation was unaffected for mexiletine, and even increased for lignocaine. Dual exponential components of dV/dtmax recovery following a 1 s conditioning depolarisation after admixture of mexiletine or lignocaine to aprindine suggest their competitive interaction on cardiac sodium channels. CONCLUSION: A combination of class I antiarrhythmic drugs having high affinity for the inactivated state of sodium channels may cause a reductive effect on dV/dtmax through competitive displacement from common receptors.

Animals↗

Combined class I antiarrhythmic agents have differential effects on tonic and use dependent block of maximum rate of depolarisation of action potentials in guinea pig cardiac muscle.

OBJECTIVE: The aim was to study the difference between tonic and use dependent block of the cardiac sodium channel produced by the combined application of the same subclass of antiarrhythmic agents (class Ia or Ib). METHODS: Conventional glass microelectrode technique was used to record the maximum rate of depolarisation (dV/dtmax) of action potentials reflecting sodium channel availability, before and after the combined application of quinidine plus disopyramide, aprindine plus lignocaine, aprindine plus mexiletine, and lignocaine plus mexiletine. Guinea pig papillary muscles (n = 4-8 per experiment) were used for the study. RESULTS: All combinations increased tonic block additively compared to use of a single drug. On the other hand, use dependent block was increased by the combination of quinidine 10 microM plus disopyramide 30 microM compared to a single drug, and was not changed by lignocaine 50 microM plus mexiletine 20 microM, whereas it was decreased by aprindine 3 microM plus lignocaine 50 microM or mexiletine 20 microM. When concentrations of mexiletine and lignocaine were increased, both tonic and use dependent block in a single drug were increased dose dependently, whereas the combination produced an additive increase in tonic block but no change in use dependent block compared to a single drug. CONCLUSIONS: The results suggested that the binding and unbinding process of the drug to produce tonic block was different from that to produce use dependent block, and that combination of different drugs produced diverse effects on use dependent block even though state dependent affinity of individual drugs seemed similar. These two factors must be born in mind in evaluating the combination therapy.

Action Potentials↗

Frequency dependent effects of class I antiarrhythmic agents studied in patients with implanted pacemakers.

Use and frequency dependency are common properties of Class I antiarrhythmic agents, which block cardiac sodium channels in vitro. The purpose of this study was to examine the rate dependent effects of Class I agents on ventricular conduction in humans in a crossover fashion. Twelve patients with implanted pacemakers who required antiarrhythmic therapy were studied. Four Class I agents were administered as follows: lidocaine, 1 mg/kg bolus followed by 4 mg/min infusion; disopyramide, 1 mg/kg bolus followed by 0.02 mg/kg per hour; aprindine, 1 mg/kg bolus followed by 4 mg/min infusion; and flecainide, 100 mg/day orally for 1 week. Trains of ventricular test stimuli between 70-180 ppm were applied during stable VVI pacing at 60 ppm. QRS duration was determined using signal-averaged as well as standard ECGs. Lidocaine produced significant QRS prolongation at rates > 110 ppm (3.0% +/- 1.4% at 120 ppm, P < 0.05; 7.2% +/- 1.8% at 180 ppm, P < 0.01). Aprindine, disopyramide, and flecainide produced significant QRS prolongation at rates as low as 70 ppm and in a frequency dependent manner: 12.7% +/- 1.5%, 9.6% +/- 1.6%, and 13.3% +/- 2.8% at 70 ppm, respectively, (P < 0.01); 21.6% +/- 0.6%, 14.7% +/- 2.4%, and 29.9% +/- 4.2% at 180 ppm, respectively, (P < 0.01). Time constants of the single exponential development of QRS prolongation when the pacing rate was abruptly increased to 150 ppm were 0.09 +/- 0.02 sec for lidocaine, 5.1 +/- 1.2 sec for aprindine, 8.1 +/- 1.7 sec for disopyramide, and 11.9 +/- 1.4 sec for flecainide.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

Transport to intestinal lumen and peritoneal cavity of intravenously administered aprinidine in rats.

Transfer of aprindine from the blood into the intestinal lumen or into the peritoneal cavity was examined after intravenous administration of the drug at a dose of 5 mg/kg in rats. The amount of the drug transferred from the blood into the intestinal lumen was much greater than into the peritoneal cavity. The average amounts of aprindine transported into the intestinal lumen and the peritoneal cavity were 0.12 and 0.03% of the dose (5 mg/kg) in 120 min, respectively. Thus, a notable difference in the clearance values of the drug was obtained between the intestinal lumen (14.8 ml/h) and the peritoneal cavity (4.94 ml/h). The net water flux showed that secretion predominated in the peritoneal transport while absorption overbalanced secretion in the intestinal transport. It seems likely that a solvent drag effect by water movement did not contribute much to the transport of aprindine from the blood to the intestinal lumen or the peritoneal cavity. The differences in transport across the two membranes could be due to differences in the surface area and other geometrical factors. Differences could also be due to a difference in the pharmacologic effects of the drug which causes a decrease in tissue splanchnic perfusion.

Animals↗

[A case of repetitive monomorphic ventricular tachycardia].

We present a case treated with aprindine and metoprolol combined with a DDD type pacemaker for repetitive monomorphic ventricular tachycardia. A 50-year-old man was admitted because of palpitation and near syncope attack. Electrocardiogram showed repetitive monomorphic ventricular tachycardias (RBBB LAD type) and R-R interval of about 440 msec and I degree A-V block in sinus rhythm. Electrophysiologic study disclosed that overdrive pacing in HRA suppressed ventricular tachycardias. Left ventriculography revealed a dilated left ventricular and decreased contractility. Antiarrhythmic agents such as quinidine sulfate, procainamide, disopyramide, mexiletine, lidocaine and propranolol were not effective. But, the combination of propranolol and aprindine decreased the rate of the ventricular tachycardia. With aprindine 60 mg/day and metoprolol 60 mg/day combined with the atrioventricular sequential pacing at 85/min, ventricular tachycardia completely disappeared.

Aprindine↗

Electrophysiological effects of sodium channel blockers on guinea pig left atrium.

The electrophysiological effects of five sodium channel blockers (mexiletine, lidocaine, disopyramide, aprindine and flecainide) on the guinea pig left atrium were investigated by recording the action potential and its maximum rate of rise (Vmax). The onset and offset kinetics of use-dependent block of Vmax were analyzed. Lidocaine, aprindine and flecainide were classified clearly as fast, intermediate and slow, respectively. Mexiletine and disopyramide had two components in onset and offset of use-dependent block. Mexiletine showed fast and intermediate kinetics, whereas disopyramide showed intermediate and slow kinetics. Action potential duration at 90% repolarization (APD) was prolonged by disopyramide and mexiletine. The other drugs did not change the action potential duration. Effective refractory period was prolonged by all drugs with relative potency in the following order: disopyramide greater than mexiletine greater than lidocaine greater than aprindine = flecainide. In conclusion, the modes of actions of sodium channel blockers on the atrium were disclosed to be different from those on the ventricle. The pharmacological therapy for atrial arrhythmias should be based on the electrophysiological effects of the drugs on the atrium, not on the ventricle.

Action Potentials↗

Hepatocellular peroxisomes in human alcoholic and drug-induced hepatitis: a quantitative study.

The peroxisomes in the liver of four patients with alcoholic hepatitis and in six patients with drug-induced hepatitis are compared to eight control livers by catalase cytochemistry and morphometry. A decrease of catalase activity is observed in alcoholic, amitriptyline, aprindine, clomipramine and methiomazole hepatitis. Peroxisomes with a heterogeneous distribution of the catalase reaction product are found in most hepatitis livers. The number of organelles is increased 1.5 to 4.2 times in alcoholic, aprindine, methimazole and phenytoin hepatitis livers. In the last case, peroxisomes are also smaller. Changes in shape are seen in all hepatitis livers; they include invaginations, tails, funnel-like constrictions and gastruloid cisternae. In aprindine, phenytoin, methimazole and two alcoholic hepatitis livers, surface density exceeds the upper control value. These data indicate a loss of catalase activity in most hepatitis livers but also peroxisomal proliferation and shape modifications. It has been proposed that the latter changes are favorable for metabolic activity.

Biopsy↗

Cardioprotective effects of various class I antiarrhythmic drugs in canine hearts.

This study was designed to clarify the cardioprotective effects of various class I antiarrhythmic drugs, i.e., aprindine, disopyramide, flecainide, lidocaine, mexiletine, pentisomide and propafenone, on the ischemic heart. Sixty-one adult mongrel dogs were classified into eight groups according to premedication: 1) control group, physiologic saline solution was administered intravenously 25 min before left anterior descending coronary artery ligation; 2) aprindine group, 3 mg/kg body weight of aprindine intravenously; 3) disopyramide group, 2 mg/kg of disopyramide intravenously; 4) flecainide group, 2 mg/kg of flecainide intravenously followed by drip infusion of 100 micrograms/kg per min; 5) lidocaine group, 2 mg/kg of lidocaine intravenously followed by drip infusion of 100 micrograms/kg per min; 6) mexiletine group, 3 mg/kg per min of mexiletine intravenously followed by drip infusion of 15 micrograms/kg per min; 7) pentisomide group, 5 mg/kg intravenously; and 8) propafenone group, 2 mg/kg intravenously. Arterial blood pressure and electrocardiogram were monitored throughout the experiment. Two hours after coronary occlusion, the heart was excised. Myocardial mitochondria were prepared and mitochondrial function (the respiratory control index and the rate of oxygen consumption in state III) was measured polarographically. Fractionation of myocardial tissues was performed and the lysosomal enzyme (N-acetyl-beta-glucosaminidase and beta-glucuronidase) activities among fractions were measured. No significant hemodynamic changes were observed compared with the control group except for those in the disopyramide and flecainide groups; that is, decrease in heart rate without changes in blood pressure compared with the control group was observed. All antiarrhythmic drugs effectively prevented the development of ventricular arrhythmias associated with ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗

Effect of class I antiarrhythmic agents on slow Ca2+ channels of myocardial cells.

The effects of several class I antiarrhythmic drugs (aprindine, cibenzoline, disopyramide, mexiletine, lidocaine, tocainide and 711389-S) were studied on slow Ca2+ channels of rabbit sinus node cells using a double microelectrode voltage clamp technique. All these drugs decreased the heart rate, the maximum rate of rise (Vmax), the action potential amplitude and the slope of the phase 4 depolarization in spontaneously beating sinus node preparations. The order of inhibitory potency on the heart rate was: aprindine greater than 711389-S greater than cibenzoline greater than or equal to disopyramide greater than mexiletine greater than or equal to lidocaine greater than tocainide. On the current systems, these drugs decreased the slow inward current (Isi) and the time-dependent potassium current (Ik). However, the major effect was a reduction of Isi. These agents also exerted a frequency-dependent block of Isi. Furthermore, comparing the effects of class I antiarrhythmic agents on slow Ca2+ channels, the order of inhibitory effect on Vmax of sinus node cells was: aprindine greater than 711389-S greater than cibenzoline greater than or equal to disopyramide greater than mexiletine greater than lidocaine greater than tocainide. These electrophysiological observations suggest that class I antiarrhythmic drugs have a depressant effect on slow Ca2+ channels as well as fast Na+ channels of myocardial cells, and that so-called "slow" kinetic drugs may depress slow Ca2+ channels more strongly than "fast" kinetic drugs.

Animals↗

Kinetics of frequency-dependent conduction delay by class I antiarrhythmic drugs in human atrium.

We investigated use-dependent prolongation of interatrial conduction time (IACT) by class I antiarrhythmic drugs in 16 patients. Changes in IACT at the initiation of atrial pacing were used to evaluate the onset kinetics. We examined recovery kinetics by giving a single extra stimulus with a varying coupling interval after discontinuing train stimulation. Time constants of the onset kinetics were 1.52 +/- 0.15/n(fast) and 0.087 +/- 0.031/n(slow) for mexiletine, 0.075 +/- 0.015/n for aprindine, 0.078 +/- 0.019/n for disopyramide, and 0.050 +/- 0.006/n for pilsicainide. The recovery time constants were 203 +/- 66 ms for mexiletine, 1,021 +/- 162 ms for aprindine, 993 +/- 101 ms for disopyramide, and 2,930 +/- 569 ms for pilsicainide. Class I antiarrhythmic drugs produced use-dependent IACT prolongation in humans, with characteristic kinetics for each agent similar to that of depression of the maximum upstroke velocity of cardiac action potential (Vmax) reported in in vitro studies.

Anti-Arrhythmia Agents↗

Nonlinear mixed effects model analysis of the pharmacokinetics of routinely administered bepridil in Japanese patients with arrhythmias.

This study was performed to evaluate variability in the pharmacokinetics of bepridil in 38 Japanese patients with arrhythmias, and to investigate the effects of aprindine as well as CYP2D6 and CYP3A5 polymorphisms on the oral clearance of bepridil. We determined the polymorphic alleles of CYP2D6 and CYP3A5 in each subject. The plasma concentration of bepridil at steady-state following repetitive oral administration was measured with an HPLC-based method, and the oral clearance was estimated using the nonlinear mixed effects model (NONMEM) program. Mean oral clearance was significantly greater in the patients with the CYP2D6*10 allele than in those without it. On the other hand, no significant effect of the CYP3A5 polymorphism was observed on the pharmacokinetics of bepridil. In addition, aprindine seemed to reduce the oral clearance of bepridil in the patients with the CYP2D6*10 allele.

Adult↗

Evaluation of antiarrhythmic drug efficacy using holter electrocardiographic technique.

This study was performed to investigate spontaneous variability in VPC frequency, to determine standards for distinguishing antiarrhythmic efficacy from the spontaneous variability, and to compare the effectiveness of disopyramide, mexiletine, aprindine, propranolol, and diltiazem. Holter ECG techniques were used for this study and the population studied consisted of 182 patients having more than 1000 VPCs/day. Forty patients had ischemic heart disease, 52 had miscellaneous heart disease and 90 were free of heart disease (idiopathic VPCs). Circadian variability of VPCs can be divided into 4 types; Type D (VPCs increasing during waking hours), Type DN (small VPC changes between waking and sleeping hours), Type N (VPCs increasing during sleeping hours) and Type Ir (irregularly occurring VPCs). The incidence of Type D, DN, N and Ir was 45%, 29%, 12% and 14%, respectively. VPC frequency in the first and second recordings at a 7 up to 21 day interval was highly reproducible (r = 0.951). The percent reduction in VPC frequency necessary to distinguish true drug response from spontaneous VPC variability, corresponded to 57% with 95% confidence level, and 67% with 99% confidence level. VPCs were reduced by at least 57% in 19 out of 33 patients (58%) with disopyramide, 9 of 15 (60%) with mexiletine, 11 of 18 (61%) with aprindine, 9 of 24 (38%) with propranolol and 8 of 22 (36%) with diltiazem. Concerning Prop., it is exclusively effective to the Type D VPCs (70%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Analysis of ventricular arrhythmias in patients with dilated cardiomyopathy--relationship between the effects of antiarrhythmic agents and severity of myocardial lesions.

In order to investigate the usefulness of antiarrhythmic drugs in patients with dilated cardiomyopathy (DCM), 42 patients with DCM were studied using 24 h ambulatory ECG monitoring, echocardiography and right ventricular endomyocardial biopsy. All 42 patients had ventricular arrhythmias with a Lown's classification of grade II or greater (grade IVb, 25; IVa, 7; III, 7; II, 3). The patients with grade IV arrhythmias tended to have greater dilating of the left ventricle and more pronounced interstitial myocardial fibrosis than patients with lower grades. Following procainamide and/or disopyramide treatment the severity of the ventricular arrhythmias improved in 12 (29%) of the 42 patients, did not change in 27 patients (64%), and deteriorated in 3 patients (7%). Treatment with aprindine or mexiletine was effective in 7 (50%) of the 14 patients who did not respond to procainamide and/or disopyramide. Although there were no significant differences in left ventricular dimension and contractility between patients in each group who did and did not respond to antiarrhythmic treatment, those who did respond had less interstitial myocardial fibrosis. Thus, in the procainamide and/or disopyramide treated group the percent interstitial fibrosis in responding vs nonresponding patients was 10.3 +/- 4.1% vs 18.7 +/- 8.3% (p less than 0.05) respectively, while in the group treated with aprindine or mexiletine these figures were 13.0 +/- 3.2% vs 26.1 +/- 7.9% (p less than 0.02), respectively. In conclusion, the effect of antiarrhythmic drugs in DCM was dependent on the severity of the pathological changes in the myocardium, and antiarrhythmic drugs should be appropriately used for the management of ventricular arrhythmias in DCM.

Adult↗

Intropic effects of several antiarrhythmic drugs.

The effects of intravenous administration of several quinidine-like antiarrhythmic drugs (bunaftine, monochloroacetyl ajmaline, lidocaine, mexiletine, disopyramide, aprindine, diphenylhydantoin, procainamide) on left ventricular performance, evaluated by systolic time intervals (STI), were studied in 100 patients with atherosclerotic heart disease. The STI were measured: the pre-ejection period (PEP), the isometric contraction time (ICT), the left ventricular ejection time (LVET), corrected LVET (LVETc), and the PEP/LVET ratio. The degree of impairment of left ventricular performance was maximal after aprindine and disopyramide administration. This was demonstrated by significant increases in the PEP, ICT, and PEP/LVET and by significant decreases in LVET and LVETc, in patients in both III-IV and I-II NYHA classes. Bunaftine, monochloroacetyl ajmaline, and lidocaine induced a less marked impairment of myocardial performance, since the PEP, ICT, and PEP/LVET increases were not significant compared to controls in patients in NYHA class I-II, and since no variation of LVET and LVETc were observed. Mexiletine effects on myocardial performance appear to be intermediate between these groups of drugs. Diphenylhydantoin and procainamide, considered separately because of their effects on heart rate and blood pressure which are not possessed by the other drugs, induced significant increases of PEP in NYHA class III-IV patients. However, the effects of these 2 drugs on myocardial performance may have been underestimated, due to the concomitant hemodynamic effect of these drugs.

Ajmaline↗

Mitral-valve prolapse syndrome and recurrent ventricular tachyarrhythmias: a malignant variant refractory to conventional drug therapy.

Of 60 patients referred for management of drug-refractory ventricular tachyarrhythmias, 10 (17%) had mitral-valve prolapse. These 10 patients ranged in age from 19 to 70 years (mean, 47 years); seven were women. All 10 had recurrent ventricular tachycardia, while four had a history of ventricular fibrillation. Nine patients were refractory to propranolol in combination with one or more of the standard antiarrhythmic agents. All showed improvement with aprindine therapy. The results show that refractory malignant ventricular prolapse syndrome; patients with mitral-valve prolapse account for a rather high percentage of those patients referred with recurrent drug-refractory ventricular tachyarrhythmias; in patients with unexplained ventricular arrhythmias, mitral-valve prolapse should be considered; and aprindine may be effective for ventricular tachyarrhythmias associated with mitral-valve prolapse.

Adult↗

Design of a study to evaluate drug therapy of serious ventricular rhythm disturbances after an acute myocardial infarction.

A study was designed to investigate whether long-term use of aprindine can prevent sudden death from primary ventricular fibrillation. Patients with a proven recent myocardial infarction and malignant ventricular arrhythmias occurring late after the acute episode were asked to participate in a 1-yr, double-blind, randomized, placebo-controlled trial to suppress the rhythm disturbances observed on an ambulatory electrocardiogram. Particular care was taken to monitor drug adherence. Arrhythmia detection by ambulatory electrocardiography was used to assess drug efficacy; side-effects establish the maximum tollerated dose for each individual patient. Aprindine was therefore used under optimal circumstances. An interactive computer system served as a data base and provided the investigators and the monitoring committee with all the information required for a proper evaluation of the progress of the study.

Aprindine↗

[Accident during local anesthesia in a patient with antiarrhythmic therapy].

A side reaction of antiarrhythmic treatment in a 18-year-old patient with congestive cardiomyopathy is reported. During treatment with high doses of aprindine cerebral convulsions occurred. After ceasing the medication temporarily, a pacemaker revision was done in local anesthesia. Cerebral convulsions reappeared after injection of the local anesthetic. The patient died due to cardiac arrest. It is discussed that some amount of the local anesthetic agent (mepivacaine) was absorbed from the tissue elevating the blood level of local anesthetic drugs (aprindine and mepivacine) into the toxic range, thus producing cerebral convulsions, augmenting the stimulation threshold and depressing the automaticity of the heart. It is urged that antiarrhythmic treatment should be stopped before local anesthesia will be performed.

Adolescent↗

Effect of lorcainide, a new antiarrhythmic compound, on the changes in heart rhythm induced by intravenous injection of adenosine-5'-diphosphate in rats.

In rats, the intravenous injection of 1 mg/kg A.D.P. (adenosine-5'-diphosphate) results in transient thrombocytopenia, bradycardia and arrhythmias. Pre-treatment of the animals with the antiarrhythmic compounds lorcainide, aprindine, procaine (1.25, 2.5, 5 mg/kg i.v.) and xylocaine (5, 10, 20 mg/kg i.v.) before A.D.P. injection results in a reduction of bradycardia and a faster normalization of heart rate. All 4 compounds were equipotent in this respect, but the higher dose of xylocaine used should be stressed. The duration of irregular heart rhythm after A.D.P. injection was significantly shortened by all 4 compounds. Peak thrombocytopenia after A.D.P. administration is reduced only by lorcainide and the highest dose of aprindine, with two dose levels of xylocaine, but is not reduced by procaine. Suloctidyl (50 mg/kg orally) had no effect on any of the parameters registered. From this study we conclude that the normalization by the compounds of cardiac rate and rhythm disturbances after A.D.P. is due to their direct antiarrhythmic effect rather than to inhibition of platelet aggregation.

Acetamides↗